usb: storage: fix multi-line comment style

No functional changes here, just making sure our
storage driver uses a consistent multi-line comment
style.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>